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A wooden tripod holding an optical level is set up firmly on the ground. Levelling or leveling (American English; see spelling differences) is a branch of surveying, the object of which is to establish or verify or measure the height of specified points relative to a datum.
The Y level or wye level is the oldest and bulkiest of the older style optical instruments. A low-powered telescope is placed in a pair of clamp mounts, and the instrument then leveled using a spirit level, which is mounted parallel to the main telescope. The term dumpy level (also builder's level) endures despite the evolution in design. They ...
The commonly used datum is mean sea level. [3] Dumpy level – optical instrument used to establish or check points in the same horizontal plane. It is used in surveying and building with a vertical staff to measure height differences and to transfer, measure and set heights. Also called a builder's level or leveling instrument.
Combining a spirit level with an optical telescope results in a tilting level or dumpy level. [5] These leveling instruments as used in surveying to measure height differences over larger distances. A surveyor's leveling instrument has a spirit level mounted on a telescope (perhaps 30 power) with cross-hairs, itself mounted on a tripod. The ...
The pibal theodolite uses a prism to bend the optical path by 90 degrees so the operator's eye position does not change as the elevation is changed through a complete 180 degrees. The theodolite is typically mounted on a rugged steel stand, set up so it is level and pointed north, with the altitude and azimuth scales reading zero degrees.
The optical plummet has either a bullseye or cross-hair sight for positioning the instrument over a survey marker or ground control point. The positional accuracy from sighting through an optical plummet depends on the accuracy of the leveling, which must be performed before the final positioning.
The concept of a laser level has been around since at least the early 1970s, [2] the original spinning-mirror design laser plane and line level was patented by the late 1980s, [3] and the compact lens-based laser line level (as produced by many tool manufacturers today) was patented in the late 1990s. It was invented by Oscar Soliz in the late ...
Stadia marks on a crosshair while viewing a metric levelling rod.The top mark is at 1.500 m and the lower is at 1.345 m. The difference between the rod readings is 0.155 m, yielding a distance to the rod of 15.5 m.